We are facing a problem with black particle floating issue for fly ash based cement.Plant is using fly ash ~ 30% in PPC cement and fly ash with LOI varies from 2 to 8%. When fresh concrte is made black particle is floated on the surface. Floating particle is collected and analysed with PSD of <5 micron.Cement PSD ( 3 to 32 micron is around 58 to 60%) with 5 micron passing PSD is around 10%Plant has to use this fly ash only due to availability and cost reason.